Field of the Invention
This invention concerns a method for measuring the quality of a steam flow to a well or the like. It relates more particularly to determining the quality of wet steam used for enhancing petroleum recovery from a subterranean reservoir, which steam has a relatively low quality due to the presence of water with the steam's vaporous component.
Steam flooding has become an accepted practice in oil or petroleum recovery from marginal fields or reservoirs that require a degree of stimulation to produce a satisfactory flow of the crude petroleum. Thus, a pressing need for a simple method to determine the quality of steam at the well head of an injection well has escalated. Such a measurement, if simplified, would be particularly useful toward determining the degree of heat which is put into an underground reservoir from an external source.
The measurement or monitoring of steam quality is of importance since the steam's quality directly affects production operations. Further, the quality of the steam which can be most economically injected into a particular substrate or reservoir is contingent on a number of circumstances. The latter include for one thing, the age of the reservoir and the anticipated prospects for extracting commercially justified amounts of hydrocarbons therefrom.
In brief, it is desirable that the quality of steam which is injected into each well be altered or adjusted to a level of quality that best conforms to that well's condition.
It is known to be particularly effective in this type of stimulation operation to have the flow of injected steam monitored by use of a meter positioned in the steam carrying line. It can be appreciated, that the steam will normally leave the steam generator or source at a known quality pressure and mass flow rate. As the pressurized steam flow progresses toward an injection well, however, the quality, will usually be substantially decreased. A decrease in quality can be based on such factors as the distance between the well and the source and the degree of pipe insulation. It will further depend on the number and orientation of fittings through which the stream has to travel prior to reaching the injection port or well because of phase separation that can occur in those devices.
It is important therefore as a matter of economic practicality, that a flow monitoring and controlling means be inserted into the steam carrying conduit immediately upstream of each well head. A choke mechanism in the steam line will usually function to constrict the steam flow, whereby to allow regulation of the steam mass flow rate which enters that particular well.